The present invention relates to a roll bar structure of a vehicle, and more specifically to a roll bar structure of a vehicle equipped with an open top and a side panel forming a vehicle side face.
In recent years, a so-called open car equipped with an open top has had a roll bar which is provided over a vehicle body to protect a driver's head during a vehicle rollover. It is known that such a roll bar is connected with a reinforcement member extending in a vehicle width direction in order to increase its resistance against the vehicle rollover. For example, Japanese Patent Laid-Open Publication No. 11-115662 discloses a roll bar structure of a vehicle, in which both ends of a base portion extending in the vehicle width direction are fixed respectively to side bodies of an automotive vehicle, and both ends of a pair of reverse-U-shaped members extending upward are fixed to this base portion by welding. Also, Japanese Patent Laid-Open Publication No. 11-321334 discloses that the roll bar is attached to side panels of the vehicle via open-top supporting brackets in order to increase an attaching strength of the roll bar.
In the conventional roll bar structure of a vehicle, however, since the member extending in the vehicle width direction and the roll bar extending upward are abutted and welded there, there is concern that a large load applied to the roll bar during the vehicle rollover and the like may cause the welded connection to be released and thus a resistance of the roll bar against the vehicle rollover may not increase sufficiently. Also, the roll bar is generally formed in a bent shape in order that an enough cabin space or storing space of the open top is provided, and its interference with any other equipments is avoided. Herein, it is generally difficult to connect firmly such a bent-shaped roll bar with a crossbar extending in the vehicle width direction.